All Exams Test series for 1 year @ ₹349 only
Question

If $\frac{a^2}{b^2+c^2}=\frac{b^2}{c^2+a^2}=\frac{c^2}{a^2+b^2}$, then what is the value of $a^4+b^4+c^4$ equal to ?

The correct answer is

$a^2b^2+b^2c^2+c^2a^2$

To solve the problem, we need to find the value of \( a^4 + b^4 + c^4 \) given the condition \(\frac{a^2}{b^2+c^2}=\frac{b^2}{c^2+a^2}=\frac{c^2}{a^2+b^2}\). Let's denote this common ratio as \( k \). Thus, we have the equations:

  • \(\frac{a^2}{b^2 + c^2} = k \Rightarrow a^2 = k(b^2 + c^2)\)
  • \(\frac{b^2}{c^2 + a^2} = k \Rightarrow b^2 = k(c^2 + a^2)\)
  • \(\frac{c^2}{a^2 + b^2} = k \Rightarrow c^2 = k(a^2 + b^2)\)

By summing these equations, we get:

\(a^2 + b^2 + c^2 = k[(b^2 + c^2) + (c^2 + a^2) + (a^2 + b^2)]\)

Simplifying the right side:

\(a^2 + b^2 + c^2 = k[2(a^2 + b^2 + c^2)]\)

Thus:

\(1 = 2k \Rightarrow k = \frac{1}{2}\)

Substituting back, we have:

  • \(a^2 = \frac{1}{2}(b^2 + c^2)\)
  • \(b^2 = \frac{1}{2}(c^2 + a^2)\)
  • \(c^2 = \frac{1}{2}(a^2 + b^2)\)

Additionally, adding these equations yields:

\(a^2 + b^2 + c^2 = \frac{1}{2}[2(a^2 + b^2 + c^2)] = a^2 + b^2 + c^2\)

This confirms our value of \( k \). Now, consider each of the original squared expressions:

By plugging \( a^2 = \frac{1}{2}(b^2 + c^2) \), \( b^2 = \frac{1}{2}(c^2 + a^2) \), and \( c^2 = \frac{1}{2}(a^2 + b^2) \) into \( a^4 + b^4 + c^4 \), we can show:

\(a^4 + b^4 + c^4 = \left(\frac{1}{2}(b^2 + c^2)\right)^2 + \left(\frac{1}{2}(c^2 + a^2)\right)^2 + \left(\frac{1}{2}(a^2 + b^2)\right)^2\)

By simplifying, each squared term yields:

\(\frac{1}{4}(b^4 + 2b^2c^2 + c^4), \frac{1}{4}(c^4 + 2c^2a^2 + a^4), \frac{1}{4}(a^4 + 2a^2b^2 + b^4)\)

Summing all the expanded squared terms gives:

\(\frac{1}{4}(2a^4 + 2b^4 + 2c^4 + 2(a^2b^2 + b^2c^2 + c^2a^2)) = a^2b^2 + b^2c^2 + c^2a^2\)

Thus, the value of \( a^4 + b^4 + c^4 \) is \( a^2b^2 + b^2c^2 + c^2a^2 \). Therefore, the correct option is:

Option 3: \( a^2b^2 + b^2c^2 + c^2a^2 \)

Was this answer helpful?

Important Questions from Algebra

  1. If 2x – y = 2 and xy =  \(\frac{3}{2}\) , then what is the value of x 3–  \(\frac{{{y^3}}}{8}\) ?

  2. If (10a 3+ 4b 3) : (11a 3- 15b 3) = 7 : 5, then (3a + 5b) : (9a - 2b) =?

  3. If 4sin 2 θ = 3(1+ cos θ), 0° < θ < 90°, then what is the value of (2tan θ + 4sin θ - sec θ)? 
  4. The value of:

    \(\frac{{\sin 23^\circ \cos 67^\circ + \sec52^\circ \sin38^\circ + \cos 23^\circ \sin 67^\circ + \rm cosec52^\circ \cos 38^\circ }}{{\rm cose{c^2}20^\circ - {{\tan }^2}70^\circ }}\)

  5. If (x + y) 3+ 27(x - y) 3= (Ax - 2y)(Bx 2+ Cxy + 13y 2), then the value of A - B - C is:

Need Expert Advice?

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App